/*
 *  Licensed to the Apache Software Foundation (ASF) under one or more
 *  contributor license agreements.  See the NOTICE file distributed with
 *  this work for additional information regarding copyright ownership.
 *  The ASF licenses this file to You under the Apache License, Version 2.0
 *  (the "License"); you may not use this file except in compliance with
 *  the License.  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 *  Unless required by applicable law or agreed to in writing, software
 *  distributed under the License is distributed on an "AS IS" BASIS,
 *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *  See the License for the specific language governing permissions and
 *  limitations under the License.
 */

package org.apache.coyote.http11.filters;

import java.io.IOException;
import java.io.OutputStream;
import java.util.zip.GZIPOutputStream;

import org.apache.tomcat.util.buf.ByteChunk;

import org.apache.coyote.OutputBuffer;
import org.apache.coyote.Response;
import org.apache.coyote.http11.OutputFilter;

/**
 * Gzip output filter.
 * 
 * @author Remy Maucherat
 */
public class GzipOutputFilter implements OutputFilter {

	// -------------------------------------------------------------- Constants

	protected static final String ENCODING_NAME = "gzip";
	protected static final ByteChunk ENCODING = new ByteChunk();

	/**
	 * Logger.
	 */
	protected static org.apache.juli.logging.Log log = org.apache.juli.logging.LogFactory
			.getLog(GzipOutputFilter.class);

	// ----------------------------------------------------- Static Initializer

	static {
		ENCODING.setBytes(ENCODING_NAME.getBytes(), 0, ENCODING_NAME.length());
	}

	// ----------------------------------------------------- Instance Variables

	/**
	 * Next buffer in the pipeline.
	 */
	protected OutputBuffer buffer;

	/**
	 * Compression output stream.
	 */
	protected GZIPOutputStream compressionStream = null;

	/**
	 * Fake internal output stream.
	 */
	protected OutputStream fakeOutputStream = new FakeOutputStream();

	// --------------------------------------------------- OutputBuffer Methods

	/**
	 * Write some bytes.
	 * 
	 * @return number of bytes written by the filter
	 */
	public int doWrite(ByteChunk chunk, Response res) throws IOException {
		if (compressionStream == null) {
			compressionStream = new FlushableGZIPOutputStream(fakeOutputStream);
		}
		compressionStream.write(chunk.getBytes(), chunk.getStart(), chunk
				.getLength());
		return chunk.getLength();
	}

	// --------------------------------------------------- OutputFilter Methods

	/**
	 * Added to allow flushing to happen for the gzip'ed outputstream
	 */
	public void flush() {
		if (compressionStream != null) {
			try {
				if (log.isDebugEnabled()) {
					log.debug("Flushing the compression stream!");
				}
				compressionStream.flush();
			} catch (IOException e) {
				if (log.isDebugEnabled()) {
					log
							.debug(
									"Ignored exception while flushing gzip filter",
									e);
				}
			}
		}
	}

	/**
	 * Some filters need additional parameters from the response. All the
	 * necessary reading can occur in that method, as this method is called
	 * after the response header processing is complete.
	 */
	public void setResponse(Response response) {
	}

	/**
	 * Set the next buffer in the filter pipeline.
	 */
	public void setBuffer(OutputBuffer buffer) {
		this.buffer = buffer;
	}

	/**
	 * End the current request. It is acceptable to write extra bytes using
	 * buffer.doWrite during the execution of this method.
	 */
	public long end() throws IOException {
		if (compressionStream == null) {
			compressionStream = new FlushableGZIPOutputStream(fakeOutputStream);
		}
		compressionStream.finish();
		compressionStream.close();
		return ((OutputFilter) buffer).end();
	}

	/**
	 * Make the filter ready to process the next request.
	 */
	public void recycle() {
		// Set compression stream to null
		compressionStream = null;
	}

	/**
	 * Return the name of the associated encoding; Here, the value is
	 * "identity".
	 */
	public ByteChunk getEncodingName() {
		return ENCODING;
	}

	// ------------------------------------------- FakeOutputStream Inner Class

	protected class FakeOutputStream extends OutputStream {
		protected ByteChunk outputChunk = new ByteChunk();
		protected byte[] singleByteBuffer = new byte[1];

		public void write(int b) throws IOException {
			// Shouldn't get used for good performance, but is needed for
			// compatibility with Sun JDK 1.4.0
			singleByteBuffer[0] = (byte) (b & 0xff);
			outputChunk.setBytes(singleByteBuffer, 0, 1);
			buffer.doWrite(outputChunk, null);
		}

		public void write(byte[] b, int off, int len) throws IOException {
			outputChunk.setBytes(b, off, len);
			buffer.doWrite(outputChunk, null);
		}

		public void flush() throws IOException {
		}

		public void close() throws IOException {
		}
	}

}
